Solid-state light emitting elements such as light emitting diodes (LEDs) may be used to cure photosensitive media such as coatings, inks, adhesives, and the like. Effective curing of photosensitive materials involves uniformly irradiating light from LEDs on to the photosensitive material in order to mitigate under-curing or over-curing over a desired target area. The inventors herein have recognized potential issues with the above conventional lighting systems and methods. Namely, LEDs generally emit light in a hemispherical pattern, and may not irradiate the entire target area, which may be rectangular or otherwise non-hemispherically shaped, uniformly enough to mitigate under-curing or over-curing. Furthermore, coupling optics such as reflectors, which may be used in conjunction with LEDs to reflect the emitted light towards the target area, suffer from retro-reflection of light at the reflector corners, causing shadowing at the corners of the radiant output and can lead to under-curing portions of the target area.
One approach that may at least partially addresses the above issue includes a lighting device comprising a light emitting element and a reflector, the reflector comprising: a first opening surrounding the light emitting element and a second opening; reflector side walls forming the first and second openings; the reflector side walls divergently extending from the first opening away from the light emitting element to the second opening; and corner facets, wherein each corner facet is positioned over a corresponding reflector corner formed by an adjacent pair of reflector side walls at the first opening.
In another embodiment, a lighting method may comprise: emitting light from a light emitting element about a central axis on to a work piece; positioning a tapered reflector between the light emitting element and the work piece, wherein light emitted through the first opening and incident at tapered reflector side walls is collimated through the second opening of the tapered reflector toward the work piece about the central axis; and positioning corner facets at corresponding corners of the tapered reflector, wherein light incident at the corner facets is collimated towards the work piece about the central axis, wherein the tapered reflector side walls form the first opening proximal to the light emitting element and diverge away from the central axis towards the work piece to form the second opening, and the corresponding corners of the tapered reflector are formed by an intersection of an adjacent pair of reflector side walls and the first opening.
In another embodiment, a lighting device may comprise an array of light emitting elements, and a tapered frustum reflector having a shape aspect, the frustum reflector comprising: first and second openings having an opening shape corresponding to the shape aspect; reflector side walls joined to form the first and second openings, a number of reflector side walls corresponding to the shape aspect; and corner facets positioned at corners formed by intersection of adjacent reflector side walls and the first opening, a number of corner facets corresponding to the shape aspect.
In this manner, the technical effect of uniformly irradiating a target photosensitive work piece while mitigating under-curing and over-curing may be achieved, while reducing a size of the coupling optics and reducing a distance between the light emitting elements and the work piece, thereby decreasing cure times and lowering manufacturing costs.